Bacteria Used for Wastewater Treatment

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What are the most efficient bacteria for wastewater treatment (aerobic, anaerobic and facultative)?

How can I encourage their growth and what are the ideal conditions for them? 

I'm new in a field so I'm searching for literature about biological wastewater treatment.

Taxonomy

17 Answers

  1. Dear Kristaps,

     

    Wastewater treatment - Biological treatment. Secondary treatment is the biological treatment of water using a wide variety of microorganisms, primarily bacteria. These microorganisms convert biodegradable organic matter contained in wastewater into simple substances and additional biomass.

     

    Aerobic wastewater treatment processes include treatments such as activated sludge, oxidation ditches, trickling filter, lagoon-based treatments, and aerobic digestion. Equipment may include diffused aeration systems or mechanical surface aerators, such as RWL Water’s Tornado aspirating aerators, in order to maximize oxygen transfer and minimize odors as the wastewater is treated.

     

    Anaerobic digestion is a process in which microorganisms break down biodegradable material in the absence of oxygen. It can be used to process a wide range of organic material, from food waste and grass to waste paper and animal waste digestion is used for effluent treatment in food and beverage manufacturing, as well as for treatment of municipal wastewater, chemical effluent, and agricultural waste.

     

     

    https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=15&cad=rja&uact=8&ved=0ahUKEwjNocjm5P7TAhWMvY8KHS6tDVcQFghHMA4&url=https%3A%2F%2Fwww.rwlwater.com%2Fanaerobic-digestion%2F&usg=AFQjCNE1civL3IGPxDaKU9AUu8KRS1JGjg&sig2=R6enXk0SxS6ZH6gTeicUUg

    1 Comment

    1. Hello Prem

      This is literature. He need to prove results. A very important element missing from this description: biology. How can you make with an effluent totally chemical - biological - treatment? How can we make - biological treatment - when the majority of micro organisms are dead? How can we make - biological - treatment without describing the kind of treatment as for example: treatment of purification? How can we make - biological - treatment in a short space of time too? How can we explain the production of over 45 million tonnes of residue of mud at the output of the STEP? How to explain biochemical effluent with oxygen, so - aerobic - have a space, an area that would create without oxygen? How to explain by what process an - aerobic - effluent becomes spontaneously without oxygen when it is brewed by a mechanical arm that adds air to the depths of the pool? How to explain the process by which organisms micro - aerobic - become spontaneously without oxygen? How to explain the presence of legacy organizations - aerobic-biological - pickups can survive in a chemical effluent? 

      We're simply in the Court of miracles, utopias.

      Bonjour Prem

      Tout ceci est de la litérature. Il faut pour le prouver donner des résultats. Un élément très important manque à cette description: la biologie. Comment peut-on faire du traitement -biologique- avec un effluent totalement chimique? Comment peut-on faire du traitement -biologique- quand la majorité des micros organismes sont morts? Comment peut-on faire du traitement -biologique- sans décrire le genre de traitement comme par exemple: traitement d'épuration? Comment peut-on faire du traitement -biologique- dans un espace de temps aussi court? Comment peut-on expliquer la production de plus de 45 millions de tonnes de résidus de boue en sortie des STEP? Comment expliquer un effluent biochimique contenant de l'oxygène, donc -aérobie- avoir un espace, une zone qui se créerait sans oxygène? Comment expliquer par quel processus un effluent -aérobie- devient spontanément sans oxygène quand il est brassé par un bras mécanique qui fait rentrer de l'air jusqu'au plus profond du bassin? Comment expliquer le processus par lequel des micros organismes -aérobie- deviennent spontanément sans oxygène? Comment expliquer la présence de micros organismes d'origine -aérobie- -biologique- puissent survivre dans un effluent chimique? 

      On est tout simplement dans la cour des miracles, des utopies.

       

  2. In municipal wastewater treatment, primary wastewater treatment is the biological treatment process, and it refers to the removal of nitrogen compounds, primarily ammonium salts.  This is a three-stage process with two different sets of environmental conditions required.  You don't need to choose the bacteria - they are already there.

    The first stage is nitrification, in which nitrifying microbes such as Nitrosomonas species bacteria oxidise ammonium into nitrites.  The second stage, also nitrification, involves microbes such as Nitrobacter species bacteria oxidising the nitrites into nitrates.  Both of these processes require a carbon source, present in municipal wastewater sludge, and oxygen.  The key to managing nitrification is maintaining sufficient oxygen levels to keep the conditions aerobic.  Dissolved oxygen levels are generally measured and controlled via aeration.

    The final stage is denitrification, in which denitrifying microbes reduce nitrates to nitrogen, which comes out of solution as a gas.  This occurs in anoxic conditions:  oxygen depleted but nitrate-rich.

    Note that this same nitrification-denitrification process is the foundation of the Berlin Method of biological treatment for marine aquaria.

    As a biological process, the stability of environmental conditions is paramount.  You can expect the microbial colonies to crash if you have an interruption of more than about four hours to the food or oxygen supply.

    There is plenty of literature available on "biological wastewater treatment".  It is, however, important to note that this only forms part of a wastewater treatment process (preliminary treatment is generally required to remove suspended inorganic solids) and that the most important thing to do is characterise your wastewater to determine the appropriate treatment methodology.  If biological treatment is an appropriate part of this treatment, the specifics of your wastewater stream are also required to determine plant capacity and design, with the biological treatment capacity determined not just by the flow rates, but also by the Biological Oxygen Demand (BOD) of your specific wastewater, dependent on both wastewater composition and age of the sludge (biological processes will be occurring before the wastewater arrives at the plant).

  4. Hi Kristaps,

    I'm working for a company which has a great experience in this field.

    We produce and manage directly bacteria for waste water plant (anaerobic, facultative, photosynthetic and so on....)

    Please write me at this address:

    m.testoni@ncr-biochemical.it  

    manu76.mt@gmail.com

  6. One of the best primers for this field of study is a classic " Microbiology for Sanitary Engineers " by Ross McKinney.  It is easy to read and full of all the pertinent information in your questions. It may be be completely up to date on newer membrane treatment schemes, but all the basics are in there.

  9. hello Kristaps,

    Generally you dont choose the type, but they are chosen based on function and your ability to detect and grow them .Dont worry about the type as of now,screen for the function that you want.As Ian Pearson says already they must be present naturally just that now a selective type be multiplied.

  10. Hi Kristaps,

    Generally you do not need to choose the bacteria you need, they are naturally there in the wastewater - they are present in our intestines and so are excreted with our faeces.  However as indicated by the contributors, the aim of the wastewater treatment process is to create optimum conditions for selected species to thrive, and to reduce the proliferation of unwanted species.  Hence in a biological nutrient removal wastewater treatment process you will create different conditions in different process units of the plant for the different species.  An anaerobic unit followed by an anoxic unit followed by an aerobic unit - each unit allowing certain species to proliferate and perform the function we want them to do.  This includes the units for stabilisation and digestion of wastewater sludges.

    In some applications, suppliers require the addition of proprietary bacterial cultures and/or enzymes from time to time to improve particular process functions for their process configurations.  These may be costly but may result in improved performance, particularly in terms of reducing the process time for breakdown of organics in the wastewater.

    Prem has given a good description of particularly the anaerobic bacteria groups, and you should read a good book on the microbiology of wastewater treatment

  11. All of the comments below have merit and awareness of their expertise.  Several things must be brought up.

    1. No decisions on any approach can be made until you get a DNA of the microbes present in the current conditions. 

    2. You must take into consideration the Temperature of the Water and therefore the best species of Microbes that will work in these conditions.

    3. Use a DO meter to measure the amount of DO in the system. There are methods to increase the DO (Dissolved Oxygen) which will excite the exponential growth of the Microbes.

    4.  Take a vertical profile of the sludge and dirty water (high TSS) levels of the system and send to your lab for evaluation of what is present in this system, such as Nitrogen, Phosphorus, etc, etc... 

    5. once you have a cross section of what is in there, you can then begin to approach a cure for what ails you.  I believe you will have to supply both aerobic  as well as anaerobic Microbes.

  12. Obligate aerobes need oxygen to grow. In a process known as cellular respiration, these  organisms use oxygen to oxidize substrates (for example sugars and fats) and generate energy. Facultative anaerobes  use oxygen if it is available, but also have  anaerobic methods of energy production. An  anaerobic  organism or anaerobe is any organism that does not require oxygen for growth. It may react negatively or even die if oxygen is present. (In contrast, an  aerobic  organism (aerobe) is an organism that can survive and grow in an oxygenated environment.)

    • Anaerobic bacteria do not grow on solid media in room air (0.04% carbon dioxide and 21% oxygen).
    • Facultative anaerobic bacteria can grow in the presence as well as in the absence of air.
    • Microaerophilic bacteria do not grow at all aerobically or grow poorly, but grow better under 10% carbon dioxide or anaerobically.
    • Anaerobic bacteria can be divided into strict anaerobes that can not grow in the presence of more than 0.5% oxygen and moderate anaerobic bacteria that are able of growing between 2 to 8% oxygen.
    • Anaerobic bacteria usually do not possess catalase, but some can generate superoxide dismutase which protects them from oxygen.
    • The clinically important anaerobes in decreasing frequency are:
      • 1. Six genera of Gram-negative rods (Bacteroides, Prevotella, Porphyromonas, Fusobacterium, Bilophila and Sutterella spp.);
      • 2. Gram-positive cocci (primarily Peptostreptococcus spp.);
      • 3. Gram-positive spore-forming (Clostridium spp.) and nonspore-forming bacilli (Actinomyces, Propionibacterium, Eubacterium, Lactobacillus and Bi?dobacterium spp.); and
      • 4. Gram-negative cocci (mainly Veillonella spp.) .
    • Because of their fastidious nature, anaerobes are hard to isolate and are often not recovered from infected sites.

    Enhancement  was studied by measuring the relative increase in CFU of the two bacterial components inducing subcutaneous abscesses in mice. It is apparent that the growth rate of facultative and  aerobic bacteria  is  enhanced  much more in mixed infections with Bacteroides spp. than that of their  anaerobic  counterparts. Hypoxia offers the potential for  anaerobic bacteria  colonization and tumor destruction by the bacteria , and dormant spores of wild-type Clostridium perfringens (Cp) germinate and proliferate within the hypoxic cores of pancreatic tumors in mice.

    1 Comment

    1. Bonjour 

      Votre définition ne veut rien dire autre que venir renforcer vos dires.  

      Maintenant dites moi comment un micro organisme -aérobie- se métamorphose quand il est vient d'un milieu aérobie, qu'il vit dans un milieu aérobie?

      Comment s'instaure un milieu sans oxygène cerné de partout par un état aérobie?

      Comment se maintien un état sans oxygène quand il est entouré d'un milieu aérobie?

      Quand on établit une théorie on peut lui apporter toutes les théories possibles voir même à l'infini.

      Ceux qui prônent cette théorie oublient toujours que la nature fonctionne dans le temps et doucement.

      Il se passe automatiquement des changements lors de certaines variations d'un état qui vont engendrer des effets. Il faut déjà que la nature stabilise ce genre de modifications ce qui ne peut se faire que dans le temps.

      Hors dans votre description le temps est absent.

      le sans oxygène est une théorie  qui tient au fait qu'à l'époque les scientifiques n'arrivaient pas à définir ce qui se passait  réellement quand un milieu partait en putréfaction.

      Comme beaucoup de théories celle ci manquait de connaissance tel que la pression atmosphérique qui vient mettre à mal votre théorie.

      D'ailleurs les défenseurs de cet état vous disent tous que cela se trouve dans des endroits inncaccessibles, improuvables.

      Une simple théorie dont on peut extrapoler à l'infini lointain

      Je l'explique dans ma communication scientifique

       

      Hello your definition means nothing other that to reinforce your story.  

      Now tell me how a micro-organism - aerobic - transforms when it is just an aerobic environment, he lives in an aerobic environment?

      How builds an environment without oxygen surrounded everywhere by an aerobic State?

      How to maintain a State without oxygen when it is surrounded by an aerobic environment?

      When a theory is established we can provide all the possible assumptions even to infinity.

      Those who advocate this theory always forget that nature works in time and take it easy.

      Happens automatically changes when some variations of a State who will cause effects. They have nature to stabilize such changes which cannot be done in time.

      Off time is absent in your description.

      the without oxygen is a theory that is due to the fact that at the time scientists were unable to define what was actually happening when a middle left rotting.

      Like many theories this one lacked knowledge such as atmospheric pressure coming to bring down your theory.

      Also defenders of this State to tell you all that this is in places inncaccessibles, improuvables. 

      A simple theory which we can extrapolate to distant infinity

      I explain in my scientific communication

       

       

  13. English

     Hello you can not find better since I'm the only one at the stops to practice the - biological - treatment of wastewater.

    The approach to the management of wastewater treatment can be done only on one essential condition: the effluent must be biological characteristic.

    Then the anaerobic does not exist on Earth, the anaerobic cannot exist on our planet for the simple reason that the Earth is subject to a system of permanent reset of oxygen in any place and any area of its constitution. Where there is water, H2O there are oxygen and so in aerobic.

    The State of putrefaction is not a State without oxygen because there is water.

    The putreftion is a natural process of destruction-elimination of organic matter which takes place either in condition very oxygen and therefore can smell, without in rarefied oxygen condition and there is a release of fumes reek

     I don't know of bacteria - optional-. He should be able to explain how in what situation under what condition - erobie - normal bacteria will become Wai'anae robie or optional. It's a pure imagination of the mind when we know how sudden events atmosphere devices of all Earth sorts who have an impact on the State of any environment on our planet.

    After making necessary for a production of wastewater - born biological - it takes an of procedures which will be totally - biological-

      l do not simply as many do declare that it is but it takes all the settings - biological - born necessary to maintain the - organic - review characteristics of the medium are present.

    In the procedures of------"pit Biologique" lyseconcept are activated s 14-16 settings - biological-. A - biological - tre parameter is missing or is faulty and it and the system me who is getting balance.

    Biology is synonymous with harmony.

  14. Bonjour 

    Vous ne pouvez pas trouvez mieux puisque je suis le seul au mmonde à pratiquer l'épuration -biologique- des eaux usées.

    L'approche de la gestion d'épuration des eaux usées ne peut se faire qu'à une seule condition impérative: l'effluent doit être de caractéristique biologique.

    Ensuite l'anaérobie n'existe pas sur terre, l'anaérobie ne peut pas exister sur notre planète pour la simple raison que la terre est soumise à un système de réinitialisation permanente de l'oxygène en tout lieu et toute zone de sa constitution. Là ou il y a de l'eau, H2O il y a de l'oxygène et donc en aérobie.

    L'état de putréfaction n'est pas un état sans oxygène puisqu'il y a de l'eau.

    La putréftion est un processus naturel de destruction-élimination de la matière organique qui s'effectue soit en condition très oxygènée et donc peut d'odeur, sans en condition d'oxygène raréfiée et là il y a dégagement d'émanations pestilentielles.

    Je ne connais pas de bactérie -facultative-. Il faudrait pouvoir expliquer comment en quelle situation sous quelle quelle condition une bactérie normale -érobie- va devenir anaérobie ou facultative. C'est une pure imagination de l'esprit quand on sait comment la terre subit des manifestations atmosphériques de toutes sortes qui ont un impact certain sur l'état de tout milieu sur notre planète.

    Après avoir fait le nécessaire pour une production d'eaux usées -biologique- il faut un procédé qui lui sera totalement -biologique-.

    Il ne faut pas simplement comme beaucoup le font déclarer qu'il l'est mais il faut que tous les paramètres -biologique- nécessaires à maintenir la caractéritique -biologique- du milieu soient présent.

    Dans le procédé " Fosse Biologique"lyseconcept sont activés 14 à 16 paramètres -biologique-. Un paramètre -biologique- vient à manquer ou est défectueux et c'et tout le système qui est déséquilibré.

    La biologie est synonyme d'harmonie. 

     

  15. Its better to compare conditions to achieve aerobic and anaerobic not the bacteria. Both bacteria are good if conditions are ok. The difference is in costs, space involved to meet conditions. However there are specific advantages of anaerobic like less sludge production.

     

    1 Comment

    1. Il serait bon de définir comment il est possible d'évaluer une réduction  de production de boue.

      Comme c'est indéfinissable on reste sur une production de boue.

      La boue est une matière organique qui a vu son processus d'élimination naturelle être stoppé. 

      Une Matière organique végétale va disparaitre entre 3 à 4 semaines en bonne condition. Si durant cette phase pour quelque raison que ce soit le processus s'arrête, cette matière organique végétale se transforme en boue immédiatement. 

      Hors dans l'environnement, la boue est un élément très difficile à éliminer, qui s'évalue en temps/année.

      Une expertise sous controle d'huissier trouve 980 kg de boue dans un réservoir alimenté par 4 personnes en fonction depuis 35 ans.

      1er constat:  La boue est bien présente 

      2éme constat: Il est très difficile d'exprimer la part de matière/boue en fine particule qui a transité dans l'environnement avec le liquide.

      Idem pour les stations d'épuration qui font sècher la boue au grand air, un stock qui subit les assauts des intempéries et du vent sans oublier la quantité qui est partie avec l'écoulement du liquide lors de fortes pluies.

      Si il y avait un  réel traitement d'épuration, l'assainissement mondiale ne produirait pas plus de 45 millions de tonnes de boue d'excréments.

      Dans le procédé "Fosse Biologique"lyseconcept les excréments sont éliminés à plus de 98% avec à peine 1% de fines particules de matière fécale. Certification scientifique établie par un laboratoire.

      D'un coté nous avons des organismes internationaux qui cherchent des solutions pour éliminer ces 45 millions de tonnes de boue d'excréments, de l'autre nous avons des consultants, des experts, des scientifiques, qui ignorent ces 45 millions de tonnes de boue d'excréments.

      English

       It would be good to define how it is possible to estimate a reduction in production of mud.

      As it is indefinable we stay on a production of mud. 

      The mud is an organic matter which saw its natural elimination process be stopped. 

      A plant organic matter will disappear between 3 to 4 weeks in good condition. If during this phase for any reason the process stops, this plant organic matter turns into mud immediately. 

      1er observation: mud is well-presented 

      2nd observation: it is very difficult to express the material/mud in fine particle which has passed in the environment with the liquid. 

      Ditto for sewage treatment that are dry mud in the open air, a stock that is under the onslaught of weather and wind without forgetting the amount that is left with the flow of the liquid during heavy rains.

      If there was a real purification treatment, global sanitation would produce no more than 45 million tonnes of mud excrement.

      Out in the environment, the mud is very difficult to eliminate, something that is measured in time/year.

      Expertise under control of bailiff find 980 kilos of mud in a reservoir fed by 4 people for 35 years.

      I also note that in the statistics never appear tons of greasy mud extracted from the wastewater effluent 

      Belgian expertise shows that 2 tons of fat are in 3 days biodegradees.

       

       

       

  16. Aerobic wastewater treatment processes include treatments such as activated sludge, oxidation ditches, trickling filter, lagoon-based treatments.  Aeration is one of the first stages in the process since bacteria and other organisms require oxygen to break down organic substances in the wastewater being treated.

    1 Comment

    1. Bonjour tout ceci est de la théorie aprise dans les livres.

      Pour effectuer un traitement d'épuration -biologique- il faut impérativement que l'effluent soit totalement -biologique-

      On ne fait pas de -biologie- avec du chimique.

      C'est pour cette raison que la STEP , l'assainissement collectif produit annuellement, plus de 45 millions de tonnes de boue.

      L'épuration -biologique- élimine entièrement toutes les matières  organiques contenues dans les eaux usées.

      La boue activée: une matière organique morte ne contenant plus de bactérie vivante et dont l'aération ne sert qu'à éviter une trop forte méthanisation du milieu qui endomamgerait les résevoirs en béton.

       

      Hello all this is learn theory in books.

      To perform a treatment - biological treatment - you must that the effluent is totally - biological-

      We do not - biology - with chemicals.

      For this reason, the STEP, collective sanitation produced annually, more than 45 million tonnes of mud to excrement.

      -Biological - treatment eliminates completely all of the organic material contained in wastewater.

      Activated mud: a dead containing more live bacteria and aeration organic matter serves only to avoid too strong methanisation of the Middle who endomamgerait the resevoirs in concrete.

       

       

  17. In wastewater treatment, the general principle is to create the right conditions for the reaction you want and the bacteria will sort themselves out. Different reactions require different conditions and many of the enhancements to the basic activated sludge process have focused on adjustments to the operating conditions to make the process more efficient, by selecting for particular types of bacteria and making them work harder.

    There's a lot to learn and far too much to put in an online forum so I suggest you refer to a good general wastewater treatment textbook such as "Design & Operation of Activated Sludge Systems" by Nigel Horan, or Metcalf & Eddy's "Wastewater treatment" for more general wastewater treatment methods.

    3 Comments

    1.  Voici comment : la digestion anaérobie est un processus en trois étapes

      Pourquoi le milieu sans oxygène n'arrive t-il pas alors à éliminer les boues d'assainissement. Pourtant avec toutes ces belles théories on devrait être ultra performant.

      Here is how: ​Anaerobic ​digestion is a ​three-stage ​process

       Why the Middle without oxygen can't t - he not then to eliminate sludge sanitation. Yet with all these beautiful theories should be ultra efficient.

    2. Un effluent d'eaux usées d'assainissement collectif, est déjà dans un état biochimique. Les bactéries sont rares à moins d'être des super bactéries capables de vivre dans un tel milieu.

      Les molécules chimiques provoquent des réactions chimiques qui tuent tout être vivant.

      La boue activée n'apporte aucune action de réduction de la matière organique. Cette fonction sert uniquement à réduire les risques d'implosion du liquide sous l’effet d’une forte méthanisation du milieu au point de fissurer les bacs en béton.

      Tous les descriptifs de l'assainissement collectif définissent que l'effluent qui arrive sur le site est de la boue. La boue contient plus de 8% de bactéries mortes.

      Pour que les micros organismes puissent accomplir leur travail de  biodégradation de la matière organique, il ne faut pas que le taux de la population présente dans l’effluent, descende en dessous de 75% puisqu'à ce stade le renouvèlement est déjà compromis. La scissiparité.

      Bien entendu on est déjà largement en dessous.

      J'ai du mal au vu des débits énormes d'effluents d'eaux usées à traiter des collectifs que l'on puisse:

      Bien entendu on est déjà largement en dessous.

      J'ai du mal au vu des débits énormes d'effluents d'eaux usées à traiter des collectifs que l'on puisse 

      1 faire le tri des bactéries les plus efficaces

      2 que ces bactéries vivent et travaillent dans un milieu biochimique

      3 que le transit, tellement court, puisse laisser y avoir un soupçon de travail de biodégradation

      Dans le procédé "Fosse Biologique" lyseconcept le temps de transit est de 12 à 15 jours minimum et dans des conditions totalement -aérobie-.

      Dans les conditions générales de fonctionnement des STEP,  l'objectif a atteindre n'a jamais été d'éliminer les boues mais uniquement les bactéries, dans le liquide rejeté

       

      English 

      A mains, sewage effluent is already in a biochemical State. The bacteria are rare unless you are super bacteria able to live in such an environment.
      The chemicals cause chemical reactions that kill any living being.

      Activated mud brings no action of reduction of the organic matter. This feature is used only to reduce the risk of implosion of the liquid under the influence of a strong methanisation of the middle point of crack the concrete tubs.

      All the descriptions of collective sanitation define that the effluent that comes to the site's mud. The mud contains more than 8% of dead bacteria.

      Micros organismes are to do their job of biodegradation of organic matter, it is not the rate of the population present in the effluent, drop below 75% since at this point the renewal is already compromised. The eucaryotype.

      Of course we're already way below.

      I have trouble in view of huge flows of wastewater effluents to treat collectives that can be

    3. I prefer aerobic wastewater treatment, as there are problems with anaerobic microorganisms. Here is how:

      Anaerobic digestion is a three-stage process. In the first stage, the complex insoluble organics are hydrolyzed to simple soluble organics by the extra cellular enzymes. During this stage, the cellulose and starch are hydrolyzed to simple sugars, while proteins bifurcate into amino acids. In the second stage, called the acid phase, the acid formers (various species of Pseudomonos, Alcaligens, Flavobacterium, Escherichia and Aerobacter) convert simple organics to organic fatty acids (acetic acid). This results in higher acid concentration and low pH. In the third stage, called methane phase, methane formers utilize the organic acids and metabolized them to methane and carbon dioxide. Amino acids give rise to ammonia, which in turn, neutralize the remaining acids.

      Methane formers (species of Methanobacterium, Methanococcus and Methanosarcina) are highly frail in nature. They are strict anaerobes, grow over a wide range of temperature, difficult to cultivate and, they remain inalienable. They are highly sensitive to low pH conditions.

      These concomitant reactions in actual digestion occur simultaneously. Flawless performance of the digester will take place only when there is a balanced bacterial population of acid formers and methane formers, or, in other words, the volatile acids production equals volatile acids breakdown. If the volatile acids formation is greater than its breakdown (which usually is the case, in actual digesters), the pH lowers, inhibition or wash-out of methane formers occurs and, the process fails, biologically.

       

      P L McCarty was the one who invented anaerobic contact process in 1964. In 1969, P L McCarty and C J Young developed anaerobic filters. Lettinga invented upflow anaerobic sludge blanket (UASB) in early 1970s. UASB, and to some extent anaerobic filters found some use in India. India has a large 345 million liters per day capacity upflow anaerobic sludge blanket plant, located at Bharwara, Lucknow, Uttar Pradesh. This is the largest UASB plant in Asia.

      F H Mughal

      Karachi, Pakistan